Field
The present invention is directed to a wind turbine rotor. In particular, the present invention is directed to a modern large-scale wind turbine rotor. For the purposes of the specification, this will be defined as a wind turbine comprising a hub from which a plurality of blades project to a radius of at least 50 meters, each blade comprising a hollow fairing supported by a central spar.
Description of the Related Art
The current size of wind turbine blades is in the range of 35-55 m (radius measured from the centre of the hub to the tip of the blade). This is set to increase further in the coming years as plans are drawn up to build much larger machines for both onshore and offshore application which would require blades of size in the range of 50-100 m.
The current blade technology it scaled up ‘as is’ or with minor modifications will lead to a number of manufacturing challenges and additionally will lead to a number of design challenges for the complete turbine designer. The principal challenge is that of dealing with the very large mass of the blades which leads to very massive and therefore expensive parts for the turbine and its foundations in order to deal with the loads and in particular the fatigue loads that are placed on the turbine and its foundations.
Current blade design methodology would lead to the blade mass increasing roughly as the blade length to the power of 2.95. This is shown to be true in the case of some of the current early attempts to build large blades and is shown in FIG. 5.
In addition, as blades get larger the natural frequency of the blade drops and it becomes closer to excitation frequencies seen during operation of the turbine.